10
RELATIONSHIP BETWEEN LOG s AND LOG w AT NS-201
_
\
log s = 0.20 - 0.46 log w
OR
Oo
STANDARD DEVIATION (s) in nCilg
[
«1.58 w 0-46
L
n=5
CORRELATION IN LOG SCALE = 0.96
0.1
i.
4
pod
1
bl
10
1
20
i
pf
50
100
ALIQUOT SIZE (w) IN GRAMS
Figure 2.
Estimated Relationship Between Log s
and Log w for the Composite Soil Sample
Collected Approximately 150 ft North of
GZ at NS-201.
Suppose we want to estimate the mean Am concentration of a field sample
by withdrawing n independent aliquots of a given size w.
The variance
Va of the resulting x is s?/n.
Hence, using Equation (3) we obtain
V,=
2.5/nw* 92,
A
(5)
Now, consider the cost of counting an aliquot of soil for Am on a Ge(Li)
system. Let us assume that a counting laboratory will charge the same
rate, of,
say, K dollars per aliquot, for any aliquot size that can be
counted without special counting procedures.
Thus, we assume that the
total Am Ge(Li) analysis cost (C) for n aliquots from a field sample
does not depend on w.
That is, C = nK or
n=C/K.
(6)
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